// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_UTIL_H_
#define V8_UTIL_H_

#include "v8.h"  // NOLINT(build/include)
#include <map>
#include <vector>

/**
 * Support for Persistent containers.
 *
 * C++11 embedders can use STL containers with Global values,
 * but pre-C++11 does not support the required move semantic and hence
 * may want these container classes.
 */
namespace v8 {

typedef uintptr_t PersistentContainerValue;
static const uintptr_t kPersistentContainerNotFound = 0;
enum PersistentContainerCallbackType {
    kNotWeak,
    // These correspond to v8::WeakCallbackType
    kWeakWithParameter,
    kWeakWithInternalFields,
    kWeak = kWeakWithParameter  // For backwards compatibility.  Deprecate.
};


/**
 * A default trait implemenation for PersistentValueMap which uses std::map
 * as a backing map.
 *
 * Users will have to implement their own weak callbacks & dispose traits.
 */
template<typename K, typename V>
class StdMapTraits {
    public:
        // STL map & related:
        typedef std::map<K, PersistentContainerValue> Impl;
        typedef typename Impl::iterator Iterator;

        static bool Empty(Impl* impl) {
            return impl->empty();
        }
        static size_t Size(Impl* impl) {
            return impl->size();
        }
        static void Swap(Impl& a, Impl& b) {
            std::swap(a, b);    // NOLINT
        }
        static Iterator Begin(Impl* impl) {
            return impl->begin();
        }
        static Iterator End(Impl* impl) {
            return impl->end();
        }
        static K Key(Iterator it) {
            return it->first;
        }
        static PersistentContainerValue Value(Iterator it) {
            return it->second;
        }
        static PersistentContainerValue Set(Impl* impl, K key,
                                            PersistentContainerValue value) {
            std::pair<Iterator, bool> res = impl->insert(std::make_pair(key, value));
            PersistentContainerValue old_value = kPersistentContainerNotFound;
            if (!res.second) {
                old_value = res.first->second;
                res.first->second = value;
            }
            return old_value;
        }
        static PersistentContainerValue Get(Impl* impl, K key) {
            Iterator it = impl->find(key);
            if (it == impl->end()) {
                return kPersistentContainerNotFound;
            }
            return it->second;
        }
        static PersistentContainerValue Remove(Impl* impl, K key) {
            Iterator it = impl->find(key);
            if (it == impl->end()) {
                return kPersistentContainerNotFound;
            }
            PersistentContainerValue value = it->second;
            impl->erase(it);
            return value;
        }
};


/**
 * A default trait implementation for PersistentValueMap, which inherits
 * a std:map backing map from StdMapTraits and holds non-weak persistent
 * objects and has no special Dispose handling.
 *
 * You should not derive from this class, since MapType depends on the
 * surrounding class, and hence a subclass cannot simply inherit the methods.
 */
template<typename K, typename V>
class DefaultPersistentValueMapTraits : public StdMapTraits<K, V> {
    public:
        // Weak callback & friends:
        static const PersistentContainerCallbackType kCallbackType = kNotWeak;
        typedef PersistentValueMap<K, V, DefaultPersistentValueMapTraits<K, V> >
        MapType;
        typedef void WeakCallbackDataType;

        static WeakCallbackDataType* WeakCallbackParameter(
            MapType* map, const K& key, Local<V> value) {
            return NULL;
        }
        static MapType* MapFromWeakCallbackInfo(
            const WeakCallbackInfo<WeakCallbackDataType>& data) {
            return NULL;
        }
        static K KeyFromWeakCallbackInfo(
            const WeakCallbackInfo<WeakCallbackDataType>& data) {
            return K();
        }
        static void DisposeCallbackData(WeakCallbackDataType* data) { }
        static void Dispose(Isolate* isolate, Global<V> value, K key) {}
};


template <typename K, typename V>
class DefaultGlobalMapTraits : public StdMapTraits<K, V> {
    private:
        template <typename T>
        struct RemovePointer;

    public:
        // Weak callback & friends:
        static const PersistentContainerCallbackType kCallbackType = kNotWeak;
        typedef GlobalValueMap<K, V, DefaultGlobalMapTraits<K, V> > MapType;
        typedef void WeakCallbackDataType;

        static WeakCallbackDataType* WeakCallbackParameter(MapType* map, const K& key,
                Local<V> value) {
            return nullptr;
        }
        static MapType* MapFromWeakCallbackInfo(
            const WeakCallbackInfo<WeakCallbackDataType>& data) {
            return nullptr;
        }
        static K KeyFromWeakCallbackInfo(
            const WeakCallbackInfo<WeakCallbackDataType>& data) {
            return K();
        }
        static void DisposeCallbackData(WeakCallbackDataType* data) {}
        static void OnWeakCallback(
            const WeakCallbackInfo<WeakCallbackDataType>& data) {}
        static void Dispose(Isolate* isolate, Global<V> value, K key) {}
        // This is a second pass callback, so SetSecondPassCallback cannot be called.
        static void DisposeWeak(const WeakCallbackInfo<WeakCallbackDataType>& data) {}

    private:
        template <typename T>
        struct RemovePointer<T*> {
            typedef T Type;
        };
};


/**
 * A map wrapper that allows using Global as a mapped value.
 * C++11 embedders don't need this class, as they can use Global
 * directly in std containers.
 *
 * The map relies on a backing map, whose type and accessors are described
 * by the Traits class. The backing map will handle values of type
 * PersistentContainerValue, with all conversion into and out of V8
 * handles being transparently handled by this class.
 */
template <typename K, typename V, typename Traits>
class PersistentValueMapBase {
    public:
        Isolate* GetIsolate() {
            return isolate_;
        }

        /**
         * Return size of the map.
         */
        size_t Size() {
            return Traits::Size(&impl_);
        }

        /**
         * Return whether the map holds weak persistents.
         */
        bool IsWeak() {
            return Traits::kCallbackType != kNotWeak;
        }

        /**
         * Get value stored in map.
         */
        Local<V> Get(const K& key) {
            return Local<V>::New(isolate_, FromVal(Traits::Get(&impl_, key)));
        }

        /**
         * Check whether a value is contained in the map.
         */
        bool Contains(const K& key) {
            return Traits::Get(&impl_, key) != kPersistentContainerNotFound;
        }

        /**
         * Get value stored in map and set it in returnValue.
         * Return true if a value was found.
         */
        bool SetReturnValue(const K& key,
                            ReturnValue<Value> returnValue) {
            return SetReturnValueFromVal(&returnValue, Traits::Get(&impl_, key));
        }

        /**
         * Call Isolate::SetReference with the given parent and the map value.
         */
        void SetReference(const K& key,
                          const Persistent<Object>& parent) {
            GetIsolate()->SetReference(
                reinterpret_cast<internal::Object**>(parent.val_),
                reinterpret_cast<internal::Object**>(FromVal(Traits::Get(&impl_, key))));
        }

        /**
         * Deprecated. Call V8::RegisterExternallyReferencedObject with the map value
         * for given key.
         * TODO(hlopko) Remove once migration to reporter is finished.
         */
        void RegisterExternallyReferencedObject(K& key) {}

        /**
         * Use EmbedderReachableReferenceReporter with the map value for given key.
         */
        void RegisterExternallyReferencedObject(
            EmbedderReachableReferenceReporter* reporter, K& key) {
            DCHECK(Contains(key));
            reporter->ReportExternalReference(FromVal(Traits::Get(&impl_, key)));
        }

        /**
         * Return value for key and remove it from the map.
         */
        Global<V> Remove(const K& key) {
            return Release(Traits::Remove(&impl_, key)).Pass();
        }

        /**
        * Traverses the map repeatedly,
        * in case side effects of disposal cause insertions.
        **/
        void Clear() {
            typedef typename Traits::Iterator It;
            HandleScope handle_scope(isolate_);
            // TODO(dcarney): figure out if this swap and loop is necessary.
            while (!Traits::Empty(&impl_)) {
                typename Traits::Impl impl;
                Traits::Swap(impl_, impl);
                for (It i = Traits::Begin(&impl); i != Traits::End(&impl); ++i) {
                    Traits::Dispose(isolate_, Release(Traits::Value(i)).Pass(),
                                    Traits::Key(i));
                }
            }
        }

        /**
         * Helper class for GetReference/SetWithReference. Do not use outside
         * that context.
         */
        class PersistentValueReference {
            public:
                PersistentValueReference() : value_(kPersistentContainerNotFound) { }
                PersistentValueReference(const PersistentValueReference& other)
                    : value_(other.value_) { }

                Local<V> NewLocal(Isolate* isolate) const {
                    return Local<V>::New(isolate, FromVal(value_));
                }
                bool IsEmpty() const {
                    return value_ == kPersistentContainerNotFound;
                }
                template<typename T>
                bool SetReturnValue(ReturnValue<T> returnValue) {
                    return SetReturnValueFromVal(&returnValue, value_);
                }
                void Reset() {
                    value_ = kPersistentContainerNotFound;
                }
                void operator=(const PersistentValueReference& other) {
                    value_ = other.value_;
                }

            private:
                friend class PersistentValueMapBase;
                friend class PersistentValueMap<K, V, Traits>;
                friend class GlobalValueMap<K, V, Traits>;

                explicit PersistentValueReference(PersistentContainerValue value)
                    : value_(value) { }

                void operator=(PersistentContainerValue value) {
                    value_ = value;
                }

                PersistentContainerValue value_;
        };

        /**
         * Get a reference to a map value. This enables fast, repeated access
         * to a value stored in the map while the map remains unchanged.
         *
         * Careful: This is potentially unsafe, so please use with care.
         * The value will become invalid if the value for this key changes
         * in the underlying map, as a result of Set or Remove for the same
         * key; as a result of the weak callback for the same key; or as a
         * result of calling Clear() or destruction of the map.
         */
        PersistentValueReference GetReference(const K& key) {
            return PersistentValueReference(Traits::Get(&impl_, key));
        }

    protected:
        explicit PersistentValueMapBase(Isolate* isolate) : isolate_(isolate) {}

        ~PersistentValueMapBase() {
            Clear();
        }

        Isolate* isolate() {
            return isolate_;
        }
        typename Traits::Impl* impl() {
            return &impl_;
        }

        static V* FromVal(PersistentContainerValue v) {
            return reinterpret_cast<V*>(v);
        }

        static PersistentContainerValue ClearAndLeak(Global<V>* persistent) {
            V* v = persistent->val_;
            persistent->val_ = 0;
            return reinterpret_cast<PersistentContainerValue>(v);
        }

        static PersistentContainerValue Leak(Global<V>* persistent) {
            return reinterpret_cast<PersistentContainerValue>(persistent->val_);
        }

        /**
         * Return a container value as Global and make sure the weak
         * callback is properly disposed of. All remove functionality should go
         * through this.
         */
        static Global<V> Release(PersistentContainerValue v) {
            Global<V> p;
            p.val_ = FromVal(v);
            if (Traits::kCallbackType != kNotWeak && p.IsWeak()) {
                Traits::DisposeCallbackData(
                    p.template ClearWeak<typename Traits::WeakCallbackDataType>());
            }
            return p.Pass();
        }

        void RemoveWeak(const K& key) {
            Global<V> p;
            p.val_ = FromVal(Traits::Remove(&impl_, key));
            p.Reset();
        }

    private:
        PersistentValueMapBase(PersistentValueMapBase&);
        void operator=(PersistentValueMapBase&);

        static bool SetReturnValueFromVal(ReturnValue<Value>* returnValue,
                                          PersistentContainerValue value) {
            bool hasValue = value != kPersistentContainerNotFound;
            if (hasValue) {
                returnValue->SetInternal(
                    *reinterpret_cast<internal::Object**>(FromVal(value)));
            }
            return hasValue;
        }

        Isolate* isolate_;
        typename Traits::Impl impl_;
};


template <typename K, typename V, typename Traits>
class PersistentValueMap : public PersistentValueMapBase<K, V, Traits> {
    public:
        explicit PersistentValueMap(Isolate* isolate)
            : PersistentValueMapBase<K, V, Traits>(isolate) {}

        typedef
        typename PersistentValueMapBase<K, V, Traits>::PersistentValueReference
        PersistentValueReference;

        /**
         * Put value into map. Depending on Traits::kIsWeak, the value will be held
         * by the map strongly or weakly.
         * Returns old value as Global.
         */
        Global<V> Set(const K& key, Local<V> value) {
            Global<V> persistent(this->isolate(), value);
            return SetUnique(key, &persistent);
        }

        /**
         * Put value into map, like Set(const K&, Local<V>).
         */
        Global<V> Set(const K& key, Global<V> value) {
            return SetUnique(key, &value);
        }

        /**
         * Put the value into the map, and set the 'weak' callback when demanded
         * by the Traits class.
         */
        Global<V> SetUnique(const K& key, Global<V>* persistent) {
            if (Traits::kCallbackType != kNotWeak) {
                Local<V> value(Local<V>::New(this->isolate(), *persistent));
                persistent->template SetWeak<typename Traits::WeakCallbackDataType>(
                    Traits::WeakCallbackParameter(this, key, value), WeakCallback);
            }
            PersistentContainerValue old_value =
                Traits::Set(this->impl(), key, this->ClearAndLeak(persistent));
            return this->Release(old_value).Pass();
        }

        /**
         * Put a value into the map and update the reference.
         * Restrictions of GetReference apply here as well.
         */
        Global<V> Set(const K& key, Global<V> value,
                      PersistentValueReference* reference) {
            *reference = this->Leak(&value);
            return SetUnique(key, &value);
        }

    private:
        static void WeakCallback(
            const WeakCallbackInfo<typename Traits::WeakCallbackDataType>& data) {
            if (Traits::kCallbackType != kNotWeak) {
                PersistentValueMap<K, V, Traits>* persistentValueMap =
                    Traits::MapFromWeakCallbackInfo(data);
                K key = Traits::KeyFromWeakCallbackInfo(data);
                Traits::Dispose(data.GetIsolate(),
                                persistentValueMap->Remove(key).Pass(), key);
                Traits::DisposeCallbackData(data.GetParameter());
            }
        }
};


template <typename K, typename V, typename Traits>
class GlobalValueMap : public PersistentValueMapBase<K, V, Traits> {
    public:
        explicit GlobalValueMap(Isolate* isolate)
            : PersistentValueMapBase<K, V, Traits>(isolate) {}

        typedef
        typename PersistentValueMapBase<K, V, Traits>::PersistentValueReference
        PersistentValueReference;

        /**
         * Put value into map. Depending on Traits::kIsWeak, the value will be held
         * by the map strongly or weakly.
         * Returns old value as Global.
         */
        Global<V> Set(const K& key, Local<V> value) {
            Global<V> persistent(this->isolate(), value);
            return SetUnique(key, &persistent);
        }

        /**
         * Put value into map, like Set(const K&, Local<V>).
         */
        Global<V> Set(const K& key, Global<V> value) {
            return SetUnique(key, &value);
        }

        /**
         * Put the value into the map, and set the 'weak' callback when demanded
         * by the Traits class.
         */
        Global<V> SetUnique(const K& key, Global<V>* persistent) {
            if (Traits::kCallbackType != kNotWeak) {
                WeakCallbackType callback_type =
                    Traits::kCallbackType == kWeakWithInternalFields
                    ? WeakCallbackType::kInternalFields
                    : WeakCallbackType::kParameter;
                Local<V> value(Local<V>::New(this->isolate(), *persistent));
                persistent->template SetWeak<typename Traits::WeakCallbackDataType>(
                    Traits::WeakCallbackParameter(this, key, value), OnWeakCallback,
                    callback_type);
            }
            PersistentContainerValue old_value =
                Traits::Set(this->impl(), key, this->ClearAndLeak(persistent));
            return this->Release(old_value).Pass();
        }

        /**
         * Put a value into the map and update the reference.
         * Restrictions of GetReference apply here as well.
         */
        Global<V> Set(const K& key, Global<V> value,
                      PersistentValueReference* reference) {
            *reference = this->Leak(&value);
            return SetUnique(key, &value);
        }

    private:
        static void OnWeakCallback(
            const WeakCallbackInfo<typename Traits::WeakCallbackDataType>& data) {
            if (Traits::kCallbackType != kNotWeak) {
                auto map = Traits::MapFromWeakCallbackInfo(data);
                K key = Traits::KeyFromWeakCallbackInfo(data);
                map->RemoveWeak(key);
                Traits::OnWeakCallback(data);
                data.SetSecondPassCallback(SecondWeakCallback);
            }
        }

        static void SecondWeakCallback(
            const WeakCallbackInfo<typename Traits::WeakCallbackDataType>& data) {
            Traits::DisposeWeak(data);
        }
};


/**
 * A map that uses Global as value and std::map as the backing
 * implementation. Persistents are held non-weak.
 *
 * C++11 embedders don't need this class, as they can use
 * Global directly in std containers.
 */
template<typename K, typename V,
         typename Traits = DefaultPersistentValueMapTraits<K, V> >
class StdPersistentValueMap : public PersistentValueMap<K, V, Traits> {
    public:
        explicit StdPersistentValueMap(Isolate* isolate)
            : PersistentValueMap<K, V, Traits>(isolate) {}
};


/**
 * A map that uses Global as value and std::map as the backing
 * implementation. Globals are held non-weak.
 *
 * C++11 embedders don't need this class, as they can use
 * Global directly in std containers.
 */
template <typename K, typename V,
          typename Traits = DefaultGlobalMapTraits<K, V> >
class StdGlobalValueMap : public GlobalValueMap<K, V, Traits> {
    public:
        explicit StdGlobalValueMap(Isolate* isolate)
            : GlobalValueMap<K, V, Traits>(isolate) {}
};


class DefaultPersistentValueVectorTraits {
    public:
        typedef std::vector<PersistentContainerValue> Impl;

        static void Append(Impl* impl, PersistentContainerValue value) {
            impl->push_back(value);
        }
        static bool IsEmpty(const Impl* impl) {
            return impl->empty();
        }
        static size_t Size(const Impl* impl) {
            return impl->size();
        }
        static PersistentContainerValue Get(const Impl* impl, size_t i) {
            return (i < impl->size()) ? impl->at(i) : kPersistentContainerNotFound;
        }
        static void ReserveCapacity(Impl* impl, size_t capacity) {
            impl->reserve(capacity);
        }
        static void Clear(Impl* impl) {
            impl->clear();
        }
};


/**
 * A vector wrapper that safely stores Global values.
 * C++11 embedders don't need this class, as they can use Global
 * directly in std containers.
 *
 * This class relies on a backing vector implementation, whose type and methods
 * are described by the Traits class. The backing map will handle values of type
 * PersistentContainerValue, with all conversion into and out of V8
 * handles being transparently handled by this class.
 */
template<typename V, typename Traits = DefaultPersistentValueVectorTraits>
class PersistentValueVector {
    public:
        explicit PersistentValueVector(Isolate* isolate) : isolate_(isolate) { }

        ~PersistentValueVector() {
            Clear();
        }

        /**
         * Append a value to the vector.
         */
        void Append(Local<V> value) {
            Global<V> persistent(isolate_, value);
            Traits::Append(&impl_, ClearAndLeak(&persistent));
        }

        /**
         * Append a persistent's value to the vector.
         */
        void Append(Global<V> persistent) {
            Traits::Append(&impl_, ClearAndLeak(&persistent));
        }

        /**
         * Are there any values in the vector?
         */
        bool IsEmpty() const {
            return Traits::IsEmpty(&impl_);
        }

        /**
         * How many elements are in the vector?
         */
        size_t Size() const {
            return Traits::Size(&impl_);
        }

        /**
         * Retrieve the i-th value in the vector.
         */
        Local<V> Get(size_t index) const {
            return Local<V>::New(isolate_, FromVal(Traits::Get(&impl_, index)));
        }

        /**
         * Remove all elements from the vector.
         */
        void Clear() {
            size_t length = Traits::Size(&impl_);
            for (size_t i = 0; i < length; i++) {
                Global<V> p;
                p.val_ = FromVal(Traits::Get(&impl_, i));
            }
            Traits::Clear(&impl_);
        }

        /**
         * Reserve capacity in the vector.
         * (Efficiency gains depend on the backing implementation.)
         */
        void ReserveCapacity(size_t capacity) {
            Traits::ReserveCapacity(&impl_, capacity);
        }

    private:
        static PersistentContainerValue ClearAndLeak(Global<V>* persistent) {
            V* v = persistent->val_;
            persistent->val_ = 0;
            return reinterpret_cast<PersistentContainerValue>(v);
        }

        static V* FromVal(PersistentContainerValue v) {
            return reinterpret_cast<V*>(v);
        }

        Isolate* isolate_;
        typename Traits::Impl impl_;
};

}  // namespace v8

#endif  // V8_UTIL_H
